(1) Field of the Invention
This invention relates to an anodizing apparatus for carrying out electrolytic etching treatment on various substrates, such as semiconductor wafers, substrates for liquid crystal displays, substrates for plasma displays, substrates for organic EL devices, substrates for FEDs (Field Emission Displays), optical disk substrates, substrates for magnetic disks, substrates for magnetic optical disks, substrates for photomasks, substrates for solar cells, and substrates for micro-electro-mechanical systems (MEMS). More particularly, the invention relates to a batch processing technique for treating a plurality of substrates at the same time with high throughput.
(2) Description of the Related Art
Conventionally, an apparatus (first apparatus) of this type includes a fluororesin forming tank (2), a pair of platinum electrodes (3a, 3b), and a substrate support jig (4) for holding a substrate (1) (see Japanese Unexamined Patent Publication H5-198556 (FIGS. 1 and 2), for example).
The fluororesin forming tank (2) stores an electrolytic solution (6a, 6b). The pair of platinum electrodes (3a, 3b) are arranged, as spaced from each other, inside the fluororesin forming tank (2). The substrate support jig (4) has an opening substantially corresponding to the outside diameter of the substrate (1), and has a cutout spreadable for inserting the substrate (1) into the substrate support jig (4). The jig (4) holds the substrate (1) through a seal (5a) to be liquid-tight with respect to the electrolytic solution (6a, 6b). The substrate support jig (4) is immersed along with the substrate (1) in the electrolytic solution (6a, 6b) in the fluororesin forming tank (2). When the pair of platinum electrodes (3a, 3b) are electrified, a chemical reaction starts to render the substrate (1) porous through the opening.
Another apparatus (second apparatus) of this type includes an electrolytic solution tank (11), a pair of electrodes (14A, 14B), and a substrate support member (15) for holding a substrate (S) (see Japanese Unexamined Patent Publication No. 2003-45869 (FIGS. 1 and 3), for example).
The electrolytic solution tank (11) stores an electrolytic solution. The pair of electrodes (14A, 14B) are attached to opposite inner walls of the electrolytic solution tank (11). The substrate support member (15) has a first cassette (21) and a second cassette (22) for pinching the substrate (S) in between. The first cassette (21) has an opening (21A) substantially corresponding to the diameter of the substrate (S), and the second cassette (22) has a similar opening (22A). The first cassette (21) and second cassette (22) of the substrate support member (15) hold the substrate (S) in between, and engage the substrate (S) by pressing on peripheries of the substrate (S). The substrate support member (15) is inserted in a guide groove (16) of the electrolytic solution tank (11), the pair of electrodes (14A, 14B) are electrified, thereby causing a chemical reaction to render the substrate (S) porous through the openings (21A, 22A).
A further apparatus (third apparatus) of this type includes a lower tank portion (103), an upper tank portion (104), an anode plate (101), a silicon wafer (106), and a cathode plate (102) (see Japanese Unexamined Patent Publication H6-275598 (FIG. 1), for example).
The lower tank portion (103) and upper tank portion (104) store an electrolytic solution, and a wafer (105) under treatment is placed therebetween. The silicon wafer (106) is disposed to contact the anode plate (101) electrically, and not to contact the electrolytic solution in the lower tank portion (103). When the anode plate (101) and cathode plate (102) are electrified, a chemical reaction takes place to render the wafer (105) porous.
Since, in the third apparatus, the silicon wafer (106) keeps the anode plate (101) out of contact with the electrolytic solution, the metal of the electrode (101) does not elute in the electrolytic solution. This prevents metal contamination of the wafer (105).
However, the conventional examples with such constructions have the following problems.
In the first conventional apparatus, in order to make the substrate support jig (4) support the substrate (1), it is necessary to insert the substrate (1) in the opening after spreading the cutout of the substrate support jig (4). It is therefore difficult to make the substrate support jig (4) support the substrate (1) automatically by means of a mechanical device. When the apparatus is applied to batch processing for treating a plurality of substrates (1) at the same time, it becomes more difficult to automate the treatment in an effective way.
In the second conventional apparatus, in order to make the substrate support member (15) hold the substrate (S), it is necessary to place the substrate (S) to be pinched between the first cassette (21) and second cassette (22). Therefore, as with the first apparatus, there is a problem of being incapable of automating the treating process. Although the publication discloses an embodiment for treating two substrates (S), since the substrate support member (15) is constructed to have a considerable thickness, the apparatus is unsuitable for batch processing for treating an increased number of substrates (S).
The third conventional apparatus has the same problem as the first apparatus. In addition, since the silicon wafer (106) is made porous by the chemical reaction, it will be necessary to change the silicon wafer (106) frequently. Therefore, this apparatus has an additional problem of consuming time in maintenance to lower its operating rate.